Paste dispensing toothbrushes, such as those shown in U.S. Pat. No. 4,135,831 to Reitknecht, U.S. Pat. No. 4,269,207 to Konrad et al. and U.S. Pat. No. 4,201,490 to D'angelo, are known in the prior art but have experienced only moderate success because of several limitations of their designs. A significant limitation of these designs is that they require, at a minimum, three steps to operate. Before these brushes can be used, the hole(s) opening in the bristles must be opened, a knob at the base of the brush must be turned to dispense toothpaste into the bristles and then finally the hole(s) must be closed again. These steps require multiple manipulations of the toothbrush thus making these brushes commercially undesirable compared to using inexpensive existing toothbrushes with a separate toothpaste container.
Prior paste dispensing toothbrushes generally dispense toothpaste by using a knob at the end of the brush which rotates a cylinder on a threaded shaft. This complicated mechanism consists of several parts, is expensive to manufacture and prone to breaking.
In designs which do not have a mechanical expedient for forcing the toothpaste from the paste container, such as those which have a collapsible paste container, the units do not provide for positive dispensing of the paste and are susceptible to inadvertent dispensing of paste.
U.S. Pat. No. 5,158,383 to Glover et al. discloses a paste dispensing toothbrush with a hollow stem with a bristled head, open bottom and discharge aperture at the bristled head. A cartridge for containing paste is attached to the open bottom of the hollow stem and a hollow pump piston is disposed in the hollow stem and is slideable between an open and a closed position. A button extends through the stem and engages with the pump piston such that when the button is pressed, the pump piston simultaneously moves to the open position and dispenses paste.
However, one limitation of this design is that when the button is depressed, toothpaste can leak from the stem area back into the pump housing. This can contaminate and clog the device and make it more difficult to use. In addition, the contamination can accumulate and eventually extrude out around the button.